Aug. 1, 2011 -- Four newly identified genetic mutations may raise the risk of asthma in different ethnic groups, according to two new studies.

In the first study, researchers found that changes in the gene PYHIN1 increased the risk of asthma in people of African ancestry. In the second study, three more genetic mutations were linked to asthma in Japanese adults.

Researchers say the findings, published in Nature Genetics, are a step forward in understanding the genetic roots of asthma.

More than 300 million people worldwide have asthma, which is a chronic inflammatory disease that causes wheezing, difficulty breathing, coughing, and tightness of the chest.

New Genetic Links to Asthma

In the first study, researchers analyzed the genes of more than 18,000 people of various ethnic groups. The results showed a genetic mutation located at the gene PYHIN1 was associated with asthma in people of African ancestry.

"Asthma rates have been on the rise in recent years, with the greatest rise among African-Americans," Susan B. Shurin, MD, acting director of the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health, which co-funded the study, says in a news release. "Understanding these genetic links is an important first step toward our goal of relieving the increased burden of asthma in this population."

The study also confirmed four previously identified genes associated with asthma across all ethnic groups.

The second study looked at genes associated with asthma in 7,171 Japanese adults with asthma and a comparison group of 27,912 healthy people and identified three new genetic mutations linked to the disease.